1. Field of the Invention
The present invention relates generally to the field of construction of high concrete wall structures and, more particularly, to apparatus for vertically adjusting and aligning concrete retaining forms used in such wall construction.
2. Description of the Prior Art
High poured concrete wall structures are usually constructed in steps by pouring one horizontal wall segment atop a previously poured segment, since it is often impractical to pour the entire height of the wall structure at one time. Such incremental construction requires that the concrete retaining forms be raised from one elevation to a next and be securely fixed to the top of one horizontal wall segment before the next higher segment is poured. These concrete retaining forms may be quite large--as high as 16 feet and as long as 30 feet--and, even though constructed largely of plywood, are very heavy. Special techniques are, thereof, required for installing the forms, leveling them, and retaining them firmly in position for receiving the liquid concrete.
Usually, as each horizontal wall segment is poured, a horizontal row of outwardly projecting bolts--called she-bolts-- is installed, with the bolts on about two foot centers, at both the inside and outside of the wall, near the top of the segment. When forms are to be installed at the top of the poured segment, a crane lifts the forms, one at a time, into vertical position so that the lower form edge is slightly above the she-bolts. Leveling of the forms is accomplished by the crane operator making small positional movements of the forms and by other operators driving wedges between upper surfaces of the she-bolts and adjacent lower edges of the forms. When the forms are level, large integrated washer-nuts, referred to as catheads, are installed on the bolts. The catheads are then tightened, forcing lower edges of the form tightly against the existing wall segment, thereby retaining the forms in position. Installation is completed by conventionally tying opposing upper portions of inner and outer forms together. Later, when no longer needed, the she-bolts are unscrewed from the wall section and salvaged for re-use.
Leveling of the forms in the above described manner is difficult and hence time consuming and expensive. The great weight of the forms and the slight elasticity of their supporting cables makes small positional movements of the forms by a crane very slow and difficult, and ties up the crane for long periods of time, generally when it could be used to greater advantage elsewhere. This difficulty of the operation is generally increased after one lower corner of the form has been secured, since it is then necessary to side load the supporting cables to raise or lower the opposite corner.
And because it is difficult for a crane operator to precisely control movement of the forms, the operators installing the leveling wedges are in constant danger that their hands will be seriously injured by over movement of the forms.
For these and other reasons, there is a substantial need for an improved, faster and safer means for leveling such concrete wall forms.